The present invention is generally directed to using photoimagible polymers, such as photoresist, as temporary supports for fabricating metal interconnections with air or other dielectric materials as the insulator.
The incorporation of integrated circuits into microelectronics or computers requires a method for interconnecting the various devices with each other or with other systems. However, with the ever increasing complexity of integrated devices with greater numbers of wiring channels and the desire for packing the chips closer together to minimize transmission delays, the need for multilayer and high channel density interconnect substrates is becoming greater. The conventional approach to achieving increased interconnect density has centered on laminating together many wiring layers. This approach is typified by printed circuit board and co-fired ceramic technology. A high performance approach is exemplified by metal/polymer interconnect substrates in which multilayer wiring channels are made by sequentially patterning metals on a substrate, depositing and curing polymers on top, and removing part of the polymer for making interlayer connections as generally described in U.S. Pat. No. 4,810,332.
However, with higher interconnect wiring density, the need for using insulators with low dielectric constants becomes more important for performance reasons. For example, lowering the dielectric constant, if the geometries are kept identical, would decrease signal attenuation, current disturbance, propagation delays, and line cross-talk. Insulators with the lowest dielectric constants include space and gases such as air. Although the use of air as the dielectric is used on a very small scale in high speed gallium arsenide technology, no one had demonstrated airbridge technology in multilevel interconnect systems.